The present invention relates to switching apparatus and method for a segment of an electric power line having several phase lines. In the following text, we will refer to xe2x80x9cphase linexe2x80x9d to describe what is usually known by a person skilled in the art as xe2x80x9cphasexe2x80x9d. The apparatus and method can be used among other things but not exclusively for deicing an electric power line or even for modifying in a static or dynamic manner the power flow through an electric power line.
Known in the art, there is the U.S. Pat. No. 2,797,344 granted on Jun. 25, 1957, and naming Mr. W. T. Peirce as inventor. This patent describes an apparatus for deicing electric cables. This patent proposes that, in a power transmission line, a cable having a pair of conductors insulated from each other is provided. An electrical bridge is connected in series with one of the conductors. A means is provided for opening the electrical bridge, and another means is provided for operating the electrical bridge in response to ice accumulation on the cable. The electric bridge comprises a normally closed switch which is open by the means that responds to an ice accumulation on the cable.
Also known in the art, there is the U.S. Pat. No. 4,082,962 granted on Apr. 4, 1978, and naming as inventors Vladimir Vladimirovich BURGSDORF et al. This patent describes a device for melting the ice by direct current through conductors of an overhead power transmission line. This patent proposes the use of a rectifier that is temporarily connected to the end of one of the conductors of the line. The apparatus also comprises a grounding circuit as well as a circuit filter connected parallel to the rectifier. The circuit proposed in this patent uses a rectified current for deicing the line. For each section of the line, a rectifier, a grounding circuit and a circuit filter are used.
Also known in the art, there is the U.S. Pat. No. 4,126,792 granted on Nov. 21, 1978, and naming as inventors Georgy A. GENRIKH et al. This patent proposes a high-voltage network for areas of increased intensity of icing. This patent proposes the use of a rectifier and a switching circuit for connecting at least one conductor of the line to the rectifier so as to melt the ice by a rectified current.
Also known in the art, there is the U.S. Pat. No. 4,119,866 granted on Oct. 10, 1978, and naming as inventors Georgy Andreevich GENRIKH et al. This patent proposes the use of a direct current source and different switches connected to a segment of the line to allow a deicing of a conductor of the line by direct current.
Also known in the art, there is the U.S. Pat. No. 4,190,137 granted on Feb. 26, 1980, and naming as inventors Akira SHIMADA et al. This patent describes an apparatus for deicing trolley wires. This patent proposes to form closed loops with different segments of the trolley feeding wires and to use certain type of transformers to circulate a current through the loops which is added to the feeding current to deice the feeding wires.
Also known in the art, there is the following U.S. patents which describe different apparatuses and methods for switching lines in relation to different applications: U.S. Pat. Nos. 2,240,772; 2,852,075; 4,028,614; 4,085,338; 4,135,221; 4,322,632; 4,489,270; 4,492,880; 4,769,587; 5,124,882; 5,483,030; 5,734,256; 5,777,837; et 5,754,045.
One of the drawbacks which can be found in all of the above-mentioned switching apparatuses and methods is that none of these apparatuses and methods allows an efficient and safe switching of the conductors of a segment of an electric power line.
One of the objects of the present invention is to propose switching apparatus and method for a segment of an electric power line which allows to switch the conductors of a segment of the line without disconnecting said segment from the line, in an efficient and safe manner.
The objects, advantages and other features of the present invention will be more apparent upon the reading of the following non restrictive description of different preferred embodiments given for exemplification only in reference with the attached drawings.
According to the present invention, there is provided a switching apparatus for a segment of an electric power line having several phase lines, each of the phase lines having several conductors electrically insulated one from the other and connected in parallel for conducting a phase current, the conductors of each phase line being short-circuited among them at two ends of the segment, the apparatus comprising:
pairs of electromechanical and electronic switches connected in parallel, for selectively opening and closing the conductors of each phase line so as to conduct the corresponding phase current through one or several conductors;
detecting means for detecting current operating conditions of the segment of the electric power line; and
control means for controlling the pairs of electromechanical and electronic switches according to the current operating conditions of the segment, the switches of each pair being independently controlled by control signals.
Preferably, the detecting means comprises several load cells, at least one load cell being mounted on each phase line, each load cell comprising a load sensor for measuring a load value supported by the corresponding phase line, an inclination sensor for measuring its inclination with respect to a vertical axis, a temperature sensor for measuring an ambient temperature, and a radiofrequency transmitter for transmitting signal indicating the load value, the inclination and the ambient temperature. The detecting means also include a control unit comprising a processor having first input ports for receiving signal indicating the operating positions of the switches, and second input ports for receiving signals indicating the voltages at the terminals of the pairs of switches; a radiofrequency transmitter connected to the processor for transmitting signals indicating the operating positions of the switches, and the voltages; and electric power supply means for supplying the processor and the transmitter.
Preferably, the control means comprise the processor which further includes outputs for transmitting control signals; a radiofrequency receiver connected to the processor for receiving radiofrequency control signals from which the control signals are produced; an amplifier connected to the processor for controlling the motor means according to the control signals; and the electric power supply means for further supplying the receiver and the amplifier.
According to the present invention, there is also provided a switching method for a segment of an electric power line having several phase lines, each of the phase lines having several conductors electrically insulated one from the other and connected in parallel for conducting a phase current, the conductors of each phase line being short-circuited among them at two ends of the segment, the method comprising the following steps:
(a) detecting current operating conditions of the segment of the electric power line; and
(b) controlling pairs of electromechanical and electronic switches connected in parallel according to operating conditions detected in step (a) for selectively opening and closing the conductors of each phase line so as to conduct the corresponding phase current through one or several conductors, the switches of each pair being independently controlled by control signals.